The present invention relates to a liquid filter system, preferably an oil filter for an internal combustion engine, comprising a cup-shaped housing that is releasably connectable to a receiving head and a filter element disposed inside the housing.
Two types of fluid filters, particularly oil filters for internal combustion engines, are known in the art. On the one hand, so-called spin-on filters are used. A spin-on filter has a cup-shaped housing, a filter element non-releasably disposed therein, and a threaded end plate. The cup-shaped housing is made of metal, so that it can withstand the pressure pulsation occurring in the interior of the filter during operation of the internal combustion engine. The spin-on filter is screwed onto a receiving flange, or directly onto the engine block of the internal combustion engine, and during servicing is completely replaced with a new spin-on filter. This filter system has drawbacks, however, resulting from the material mix of the filter, because a mixture of plastics, paper, and metal must be disposed of, and separation of the various materials for disposal is problematic.
On the other hand, so-called oil modules are known in the art, in which a filter element is releasably disposed in a preferably cup-shaped housing and can likewise be screwed onto a receiving head disposed in the circuit by means of this housing. For servicing, only the metal-free filter cartridge needs to be replaced, whereas the cup-shaped housing is a lifetime component.
German Utility Model No. 200 04 31 U1 discloses a liquid filter with a bypass valve. A hollow cylindrical filter element is releasably disposed within a cup-shaped housing, and the cup-shaped housing is screwed into a connection head. A support tube, which receives the bypass valve, is disposed concentrically within the interior of the filter element. The drawback here lies in the changing of the filter element. There is a risk that the immediate surroundings of the oil filter element may be contaminated because the oil-soaked filter medium still contains a residual amount of oil, which may drip as the filter element is replaced. A further drawback is that the hands of the service personnel may become soiled by the direct contact with the oil-soaked filter element.
Another drawback is that it is not clear without closer inspection during installation of the outer housing whether a filter element is installed at all. This can be determined only by looking at the open underside of the housing, but in most cases this side has to be mounted face down, is inaccessible in an engine compartment, hidden, etc.